Power rotation of aircraft wheels



March 25, 1947. S. s. KNOX POWER ROTATION OF AIRCRAFT WHEELS Filed Dec. l8,' 1944 [NVENTOE Samue/ 5 K/70X Patented Mar. 25, 1947 UNITE s'rras Claims.

This invention has to do with a means of motor-driven rotation of aeroplane wheels preparatory to landing and specifically concerns a meth- 0d of engaging and disengaging the power drive by the action of a hydraulic piston which lifts and lowers an electric motor on which are mounted two small wheels with pneumatic tires. The general object of the present invention is to provide a simple, practical and effective method of this character.

Various means and methods of applying the motor power necessary to effect pre-rotation of the landing wheels of aeroplanes have been proposed in order that the rotational speeds of the outer parts of the tread approximate the speed of the aeroplane over the ground. Objections to these motor-driven means and methods have arisen due to the addition of considerable weight, the involved and mechanically complicated nature of the application of power to the wheels and the difficulty of removing and replacing the parts for repair.

It is a general object of my invention to provide a means for power-driven pre-rotation and a method of engaging and disengaging the power drive which will be automatic in its action, of light-weight construction, simple mechanically, without levers, clutch, rods or other heavy and cumbersome mechanical attachments, and which will require a small amount of storage space when the wheels are retracted during flight. In my present invention, the motor furnishing the power can be removed and replaced by a new driving motor in a few minutes without interfering with the wheel mechanism.

It is now general practise in building large aircraft to use a pair of medium-sized wheels and tires mounted on a single spindle or wheel axis which functions as a single wheel. This type of construction is more economical as it permits the use of smaller tires and wheels. My present invention is designed to operate on this type of wheel; however, it may easily be designed for use on a wheel on which only a single tire is mounted,

The various features and method of my inven-; tion will be fully understood from the following detailed description of a typical preferred form and application, throughout which descriptive reference is made to the accompanying drawings:

Referring in detail to the drawing, Fig. 4 is a side elevation of the upper half of the aeroplane wheel. It shows the aluminum yoke and spring steel motor-supporting bracket, also one motordriving wheel. Fig. 2 is a side elevation of a section of the aeroplane wheel-supporting column on which is mounted a small cylinder, shown in cross section, and a small pulley and steel cable, also an automatic switch. Fig. 3 is a top or plan view of Fig. 4 and shows how the power unit is held in place by the spring steel members. Fig. 1 is a front elevation taken at AA and shows the arrangement of the aluminum yoke and end view of the spring steel motor supporting members.

The operation of my invention is very simple and consists of only two working parts: First, a small electric motor I, as shown in Fig. 3, which has a driving shaft is supported by two bearings l5. On this shaft between the motor and the bearings are mounted two small wheels with pneumatic tires 2, the diameter of the tires being slightly greater than the diameter of the motor. The motor l is held by a piece of spring steel l3, which prevents it from rotating about its own axis. The bearings iii are each supported by another piece of spring steel l4 which helps hold the motor and wheels in position on the center lines of the large tires l on the aeroplane wheels. These three pieces of spring steel are fastened securely at their other ends to an aluminum yoke 3 which in turn is shown supported on the aeroplane wheel axis H5 or other suitable fixed support. The three spring steel members with the aluminum yoke are so designed that when the power unit is mounted on the aeroplane wheels, the spring steel members will be under considerable tension and will hold the motor-driving wheels 2 firmly against the large tires 11.

The other moving part is a small piston 6 which moves in a cylinder 5, see Fig. 2. The cylinder 5 shown in cross-section, Fig. 2, is mounted at some convenient place on the aeroplane wheel-supporting column or strut 4. A small pipeline I connects the bottom part of the cylinder to the hydraulic system that operates the aeroplane landing gear mechanism. Fastened to the piston 6 is a piston rod 8 which projects below the cylinder. To the lower end of this piston rod 8 is attacheda steel cab-1e l I which runs through a guiding pulley i0 and whose lower end is fastened to the motor by a small eye bolt l 2.

The motor-driving wheels and tires will be in contact with the large tires at all times except when the aeroplane is on the ground.

When the aeroplane wheels are lowered preparatory to landing, the control that operates the wheel mechanism will also operate a switch that controls current to the electric motor and the motor will start, the small tires on the wheels on the motor shaft being held firmly against the large tires will start rotating the aeroplane wheels.

The wheels will continue to rotate at a speed approaching the ground speed of the aeroplane until the tires touch the runway.

At the instant the aeroplane wheels contact the ground, the landing gear starts supporting the weight of the aircraft and the pressure in the hydraulic system increases materially. This increase in pressure acting through the small pipe line I forces the piston 6 up. This movement acting through the steel cable ll pulls and lifts the power unit away from the aeroplane tires against the tension in the spring steel supporting members, thus giving the desired free wheeling while the aeroplane is on the ground. The power unit will remain suspended in this position as long as the weight of the aeroplane is supported by its landing wheels.

On the lower end of the piston rod is mounted an automatic switch 9 as shown symbolically in Fig. 2. When the piston rod 8 moves up it breaks the electrical circuit to the motor and the motor will come to astop. Otherwise the small driving tires would continue to rotate while the aeroplane was on the ground, unless a manual control switch were installed.

When the aeroplane takes off from the ground, the above described actions are reversed. The moment the wheels of the aeroplane leave the ground, the pressure in the hydraulic system is reduced and the tension in the driving unit spring supporting bracket forces the driving motor wheels back into position on the large tires. The piston rod 8 is pulled down and the automatic switch 9 is closed. When the aeroplane wheels are retracted, the operating control turns off the electric current and the wheels stop rotating.

Referring to the drawings, no attempt has been made in any of the four views to show a connection between the wheel-supporting column and the wheels, or any electrical wiring. The reason for this is that each builder of aeroplanes uses a difierent design and it is impossible to show a composite method. The power unit, in the typical application in my drawings, is shown supported by a spring steel frame or bracket, which in turn is held in position by an aluminum yoke. In practise, it no doubt will be much easier to fasten the spring steel frame to some part of the wheel-supporting. mechanism. An automatic to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims.

Having described my invention, I claim:

1, A power drive for pre-rotation of the landing wheels of aeroplanes, comprising a hydraulic cylinder operatively connected to the hydraulic system of the aeroplane, a piston in said cylinder;

a power drive means engaging a landing wheel of the aeroplane, and means extending from said piston to said power drive means whereby actuation will retract said power drive means from engagement with the landing wheel.

2. A power drive for pro-rotation of the landin wheel of aeroplanes comprising a motor, a driving wheel engageable with a landing wheel and driven by said motor, a spring bracket attached at one end to said motor and adapted and arranged to press said driving wheel against the landing wheel, and hydraulically actuated disengaging means mounted adjacent the landing wheel and operatively connected to said motor whereby said motor and driving wheel are moved away from the landing wheel.

3. A power drive for pro-rotation of the landing wheels of aeroplanes, comprising a hydraulic cylinder operatively connected to the hydraulic system of the aeroplane, a piston in. said cylinder; a power drive means engaging a landing wheel of the aeroplane, and means extending from said piston to said power drive means whereby actuation will retract said power drive means from engagement with the landing wheel; an electric switch connected in the circuit to the power drive means, said switch being turned on or off as said hydraulic cylinder is operated.

4. A power drive for pre-rotation of the landing wheels of aeroplanes comprising a motor, a driving wheel engageable with a landing wheel and driven by said motor, a spring bracket attached at one end to said motor and adapted and arranged to press said driving wheel against the landing wheel, and hydraulically actuated disengaging means mounted adjacent the landing wheel and operatively connected to said motor whereby said motor and driving wheel are moved away from the landing wheel; a switch mounted in the motor circuit, said switch being mounted adjacent the hydraulically actuated means and operable thereby, whereby the motor is turned on and oil as the hydraulically actuated means operates.

5. A power drive for pre-rotation of the landing wheels of aeroplanes, comprising a hydraulic cylinder operatively connected to the hydraulic system of the aeroplane, a piston in said cylinder; a power drive means engaging a landing wheel of the aeroplane; a cable extending from said piston to said power drive means whereby actuation of 'said hydraulic cylinder will retract said power drive means from engaging said landing wheel.

SAMUEL S. KNOX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,377,018 Maimin May 3, 1921 1,506,440 Norris Aug. 26, 1924 627,066 Schnepf June 13, 1899 2,347,986 Bowerman May 2, 1944 2,347,847 Schnell May 2, 1944 2,288,968 Dowty July 7, 1942 

